PROJECT SUMMARY/ABSTRACT This K23 proposal will address a critical need for accessible, evidence-based behavioral sleep interventions for lower-socioeconomic status (SES) children, and will prepare the applicant, Ariel Williamson, PhD, to become an independent investigator with expertise in behavioral interventions for lower-SES children in primary care. Behavioral sleep problems, including insomnia and insufficient sleep, are associated with adverse physical, neurobehavioral, and social-emotional outcomes. Sleep problems impact 20-30% of young children and disproportionately impact lower-SES children. There is little research on behavioral sleep interventions with lower-SES youth, and no studies have examined these interventions in primary care, an accessible setting. This project will adapt and pilot Sleep Well ? Be Well, an effective behavioral sleep intervention, so that its contents and service delivery methods are appropriate for lower-SES preschoolers and the primary care context. Aim 1 is to identify attitudes, beliefs, and behaviors that are critical for adapting and implementing Sleep Well ? Be Well for lower-SES preschoolers in primary care. This aim involves collecting qualitative and quantitative data from lower-SES caregivers of preschoolers with sleep problems (N = 30) and primary care providers (N = 20 pediatricians, nurses, and integrated behavioral health clinicians [social workers and psychologists]). Aim 2 is to iteratively adapt as needed and pilot Sleep Well ? Be Well. Aim 1 results, pilot testing with lower-SES caregiver- child dyads (N = 18), and input from an advisory panel of caregivers and primary care providers will guide needed adaptations and the potential development of new approaches. Aim 3 is to conduct a pilot randomized controlled trial of the adapted intervention to examine intervention acceptability; feasibility of recruitment, randomization, and measurement procedures; treatment engagement and adherence; and the magnitude of intervention effects. Lower-SES preschoolers (N = 80) will be randomly assigned to intervention or to enhanced usual care (sleep education), with assessments of objective and caregiver-reported child sleep, as well as child behavior, at pretreatment, posttreatment, and 3-month follow-up. The proposed research and the career development plan will support Dr. Williamson?s training goals to acquire skills and knowledge in: (1) qualitative and mixed methods for intervention adaptation and development; (2) the conduct of clinical, and especially pragmatic, trials; and (3) the application of implementation science methods and frameworks to primary care research. The resources of Children?s Hospital of Philadelphia and University of Pennsylvania, and an expert team of interdisciplinary mentors and consultants, will provide an outstanding context to launch Dr. Williamson?s career. This project will also provide necessary data for Dr. Williamson?s future R01 submission of a large-scale effectiveness- implementation trial of a behavioral sleep intervention in primary care. This project aligns with NICHD?s priorities, as it focuses on behavioral intervention in primary care and behavioral health promotion for lower-SES children.